gpt-oss-20b vs Muse Spark 1.3 Contributor
Pricing, context window and real answers (November 2026)
gpt-oss-20b (OpenAI) and Muse Spark 1.3 Contributor (Meta), compared as you can actually call them on FastMetal. Both are served from the same OpenAI-compatible endpoint and API key; switching is a change to the model string.
Specs and pricing
 gpt-oss-20b |  Muse Spark 1.3 Contributor | |
|---|---|---|
| Provider | OpenAI | Meta |
| Input (per 1M tokens) | $0.0317 | $0.11 |
| Output (per 1M tokens) | $0.1477 | $0.22 |
| Typical cost (1,000 in + 500 out tokens × 1,000 calls) | $0.1055 | $0.22 |
| Context window | 131,072 tokens | 1,048,576 tokens |
| Release date | 8/5/2025 | 9/2/2026 |
| Input modalities | text | text, image, video, file, audio |
| Throughput (p50) | 114 tokens/s (n=19) | — |
| Arena · overall | #270 · ELO 1,317 | Unranked |
| Arena · Japanese | #200 · ELO 1,255 | Unranked |
| Arena · coding | #252 · ELO 1,368 | Unranked |
Prices are FastMetal's rates, before tax.
Rankings: LMArena leaderboard dataset (lmarena-ai/leaderboard-dataset), CC BY 4.0, snapshot 2026-10-28; category names mapped and ratings rounded by FastMetal.
Which should you pick?
- On price, gpt-oss-20b: $0.1477 per 1M output tokens, 33% less than Muse Spark 1.3 Contributor.
- For long documents, Muse Spark 1.3 Contributor: a 1,048,576-token context window against 131,072 for gpt-oss-20b.
- If in doubt, try both on the same key. Switching is a change to the model string, and each is billed at its own rate.
Frequently asked questions
- Which is cheaper, gpt-oss-20b or Muse Spark 1.3 Contributor?
- Per 1M output tokens, gpt-oss-20b is $0.1477 and Muse Spark 1.3 Contributor is $0.22 on FastMetal (US dollars, before tax), so gpt-oss-20b is cheaper.
- How do the context windows of gpt-oss-20b and Muse Spark 1.3 Contributor compare?
- gpt-oss-20b takes 131,072 tokens; Muse Spark 1.3 Contributor takes 1,048,576.
- Can I use gpt-oss-20b and Muse Spark 1.3 Contributor with the same API key?
- Yes. On FastMetal's OpenAI-compatible endpoint, switch by passing "gpt-oss-20b" or "muse-spark-1.3-contributor" as the model. Each is billed at its own rate from the same prepaid balance.
Try both on one API key
Create an account and add credit to call gpt-oss-20b and Muse Spark 1.3 Contributor from the browser chat and the API. No monthly fee.
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